Dry-plate rectifier unit



July 5, 1949. J. G. ABBOTT DRY PLATE RECTIFIER UNIT Filed Aug. 1, 1945 FEG.

A'KTRNEY Patented July 5, 1949 2,474,809 DRY-PLATE RECTIFIER UNIT Jerome G. Abbott, Asbury Park. N. J., assigner to the United States of America as represented by the Secretary of War Application August 1, 1945, Serial No. 608,343

2 Claims. (Cl. F75-366) (Granted under the act of March 3, 1883, as`

amended April 30, 1928; 370 O. G. 757) The invention described herein may be manufactured and used by or forv the Goverment for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to rectifiers and particularly to those of the selenium, oxide, or dryplate type.

In a particular form, conventional selenium rectiers or rectifying cells are of spaced-disc type, mounted in stacks on a common shaft adapted to hold them together and supported on a stand, all parts being open to the atmosphere. This construction is suitable for climates that have a relatively moderate humidity; but during certain seasons, or in sections of the world where the humidity is high, the selenium cells are materially and injuriously affected by the atmosphere. However, deterioration frequently takes place also from operating etlects, due to overheating. Where appreciable humidity is involved, a quasi, short-circuiting action between the plates takes place, and a permanent change and deterieration occurs that cannot be overcome practically.

The present day selenium rectiilers have particular characteristics which are outlined in various well-known technical journals, and will be further referred to later `in this specication.

'Referenceis also made, however, to the operational improvements made by this invention in the use of rectiiiers constructed in conformity therewith, and to those types of oxide or dryplate rectiers that are subject to similar conditions and structural features.

In the present invention, it is an object to pro-- vide a new and improved dry-plate rectiiier unit that will avoid one or more of the disadvantages and limitations o! the prior art.

An additional object of this invention is to provide a new and improved dry-plate rectier unit that can be kept at an optimum eiiiciency temperature, and controlled closely in this regard, to maintain a uniform operational value.

Another object of this` invention is to provide a new 'and improved dry-plate rectifier unit that vwill prevent deterioration due to atmospheric humidity and fungus growth.

Still another object of this invention is to provide a new and improved dry-plate rectifier unit that can be enectively cooled while in loperation without affecting its structural or chemical structure.

In a particular form, a rectiiler unit comprises a dry-plate rectifier cell and means for enclosing and supporting the latter. Means are provided also for cooling the rectifier and means.

It can be seen that the means can include a housing having an outer shell and an inner shell spaced therefrom, with partitions extending longitudinally to provide peripheral air ducts. The housing can also be arranged to enclose the'dryplate rectifier cell and support the same in a predetermined position; but spaced from the walls thereof to permit' access all around same. The cooling means can consist of a fluid coolant by itself, or in cooperation with an air blast of suitable nature, which may be developed by a motor and blower element of conventional form. The housing may also include means for supporting the shells.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following descripy tion taken in connection with the accompanying drawings, which are used to illustrate a particular form of the invention, while its scope will be pointed out in the appended claims.

Referring to the drawing:

Figure 1 is a side elevation of a dry-plate rectifier unit embodying this invention;

Figure 2 is a front view of Fig. 1;

Figure 3 is the rear view of Fig. 1; FlFigure 4 is a longitudinal sectional view throng Figure 5 is a -detail of the shells of the unit in exploded form;

Figure 6 is a detail of the selenium rectifier cell used in connection with this embodiment;

Figure 7 is a modified form of housing employing a corrugated-walled inner shell, and

Figure 8 is another modified' form having corrugated walls for its shells.

Similar reference characters parts throughoutv the drawing.

In the structure indicated, a particular dryplate rectiiier unit consists of a main housing il, supported onbrackets l2, that are mounted on a base member I3. The housing Il includes an outer shell I6 that is preferably of metal or heatconducting material, and of cylindrical form. An

lrefer to similar A internal or innercylindrical shell Il is concentrically placed and has peripheral ns I5 extending radially out and securing it to outer shell I6, and strengthening both shells. These iins extend longitudinally through the housing and serve as partitions, forming individual air ducts peripherally disposed around the cylinder I4. An outwardly extending flange I'I is provided at the front end, and an inwardly extending ange I8 at the rear sarasota end of the housing. The flange il is provided with bolt holes i9 which align with holes 22 in the flange of a conical funnel 25. The flange i8 has its bolt holes 2l aligned with those in the rear cover or closure 24. Bolts pass through these 1ioies to secure the funnel and cover in place, to their respective flanges il and i8. A tubular stub 26 forms a restricted oriiice for the funnel at its apex portion and has an intake flange 21 drilled with holes 28 for bolts to attach it to the outlet flange 29 of a centrifugal fan or blower 3l, that provides air under pressure. A motor 32 rotates the fan 3| through a suitable coupling. Fan and motor are .mounted on the base i3 in a conventional manner. Gaskets are used at all flanges to make a hermetically-sealed joint.

The front end of the cylinder I4 is closed with a disc-like plate closure 33, in an air and watertight manner on tightening the bolts suitablyY and also preferably by welding. A central hole 34 is suitably screw-threaded in this plate and serves to hold a clamping bolt 35 tightly when threaded into same during the placement of the conventional stacks of plate selenium of dryplate rectifying cells 36 in the inner shell. The bolt 35 also passes through the central portions of the rectiers and holds them suspended from the peripheral wall of the cylinder I4, providing a free space all around. Leads from the rectifier cells are attached to sealed terminals 38 extending through the walls of the housing. The rear end of inner-shell I4 is covered by a plate closure 24 by bolts to the flange I8. A coolant is then poured into the inner shell. This is done through a screw-threaded orifice 4l in the plate 24, by removing its plug 42, and pouring in the coolant 40, and then reinserting the plug l2 to hold it in.

The coolant iiuid 40 fills the inner shell and surrounds and intermixes among the parts of the rectifier cells, and contacts same, so as to absorb heat generated thereby in use. This fluid is preferably a liquid having a good heat-conducting action and being substantially neutral, chemically and mechanically, to the materials used in the rectifier cell. The coolant must not cause deterioration or interference in any reasonable manner with the fuctioning of the rectifier cell. For general purposes, carbontetrachloride has beeniound suitable for selenium cells. It will also absorb air suiliciently to prevent airpockets, and has other desirable features.

The operation of the device is outlined below.

Before operation, all parts of the assembly that are subject to undesirable leakage are lightened appropriately and welded over or cemented if necessary, to make such completely tight under the severest conditions of use and location. The coolant 40 is poured into the inner shell until it is completely full.

An electrical load is placed on the rectifier cell, and the fan started to blow air through the funnel against the front of the housing, -and through the peripheral air ducts 43. as indicated by the arrows. The rectifier cells, under load, heat the coolant 40, and induce convective streams, which ow against the wall of the inner shell and distribute some of their heat thereto,

and which conductively transmit same to the fins and outer shell. The air flow through the duct I3 absorbs as it leaves the housing. This air flowthat excessive high or low temperatures cause permanent changes in the chemical structure of the rectifier cell that are detrimental to its operation and life. The enclosing or housing of the rectifier cell is necessary, to enable a definite control of the temperature yto be had, as other conventional means have not been able to da so. While the enclosing of the cell prevents dissipation of the heat by extraneous atmospheric currents, it accumulates same in the coolant, so that it can be removed from the latter, in a positive and uniform manner. From a climatic point of operation, the keeping of the rectifier cells free from atmospheric humidity and variable air condition effects, including fungus growth, oxidizing and bacteriological effects, is important as such tend to deteriorate the cells and seriously interfere with their operation and permanently damage their structures. The conventional, unenclosed cells are mechanically` unprotected, which, by reason of their delicate construction and sensitivity to deterioration, tends to reduce their usefulness and increase their cost of maintenance. The housing in this invention affords the practical protection that is desirable. It also enables the unit to be handled, without specilically pick-up of the rectifier cells. The coolant 40 is a stabilizer of heat for the cells and it serves to dampen any mechanical or electrical vibration or shock that may arise in the use of the unit. It does not reduce the useful operational capacity of the cells. The terminals are arranged in an accessible manner that enables coupling to be done conveniently. In some uses, the fan element is unnecessary in the direct assembly of the unit, as an air flow can be derived from an extraneous source, or by a natural arrangement.

In the modified construction indicated in Fig. 7, the inner shell is of the form of a cylinder with a helically arranged corrugated wall 44 provided to receive the air from the fan and spread it over a long path. Its flanges and plate closures are modified to suit the corrugated walled construction of the inner shell, so they can be mounted properly and prevent leakage. The corrugated form strengthens the shell wall, gives greater cooling surfaces, internally and externally, and is easier to clear. In Fig. 8, the outer shell has a corrugated contour also.

Empirical use of selenium types of dry-plate rectifier cells, indicates that uniformity of temperature at a proper level enables them to function more efllciently and smoothly. This can be appreciated for these facts concerning the cells:

a. At a fixed voltage, the current increases with temperature rise.

b. Leakage of current in the reverse direction increases with temperature rise.

c. With increased current, there is an increase in temperature.

d. Safe temperature range is between 50 and +50 C.

e. Cells that have been stagnant for an appreciable period become less resistive, and temporarily induce high currents; this requires a controlled use for a short time, to overcome this phenomenon and return them to a normal operation condition.

f. Cells intermittently used will operate for a couple of minutes with excess leakage and then normalize.

g. The cells have a capacitive effect (0.2, mid. per sq. cm.)

h. The cells will permanently deteriorate at temperatures over 50 C.. i! their heat ls not adequaiely dissipated.

i. '10 C. is the maximum temperature which selenium cells can attain without permanent olierational damage.

The importance of having means for absorbln the heat developed in selenium cells, or dissipatlng it, can be seen from these characteristics. A positive iluid coolant in actual contact with the cells will accomplish this and act as a choke against sudden surges of temperature, while the secondary removal of heat from this coolant by' the cooling of the shell in which the coolant vcirculates serves to control the heat and temperaturev of the latter within reasonable limits. The invention provides for this in an eiiective manner and assures the use of the cells ior a long life and low maintenance. At the same time, this hermetic closure within its structure prevents damage or deterioration due to outside atmospheric conditions, such as humidity, fungus growth, and oxidizing elements.

The parts are arranged lor facile assembly and disassembly, even though in use; they may he sealed by welding or cementing at the joints. to make them tight. The term dry-plate rectifier cells throughout the specification is intended to include selenium, copper-oxide, boric aluminum.

and other plate rectiiier cells that may be made along conventional lines. and in single or plural stacks.

While there has been described'what is at.pres

ent considered to be a preferred embodiment oiy this invention, it will be obvious to those skilled in the art that various changes and further modiiications may be m'ade therein without departing from the spirit of the invention or the principles thereof. It is, therefore, intended in the appended claims to cover all such changes and modifica-v tions as fall within the true spirit and scope o! the invention.

What is claimed is:

i. A rectifier unit. comprising concentric cora cally corrugated inner and outer shells. a dry Name Date Il? 1,649,242 Ruben Nov. 1s, 1927 l 1,292,581 Peter Mar. 24, 1931 1,942,240 mcsa nb. 1s, 1934 2,024,142 Parsons nec. 1'1, 1935 2,112,133 Burnham Mar. 29, 193s 2.1mm sichert si s1. Feb. s, 1940 2,219,101 Airis spr. '1, 1942 2,200,041 Adami: June s0, 1942 v sonnen Ps'nrms 4 Number Country Date between the shells.

plate rectiiier within the inner shell, a liquid Y coolant in which the rectiiier is immersed, the outer diameter o! the inner shell being equal to the inner diameter oi the outer shell, said shells being relatively disposed so that the crests of the corrusations oi the inner shell contact the troughs o! the corrugations of the outer shell. whereby a series of separate sir ducts are provided by and JEROME G. ABBUI'I'.

REFERENCES CITED The following references are ci record in the ille ci this patent:

UNITED STATES PATENTS Number France um 1'1. 1931 

